Impression control mechanism in power driven typewriters



S. D. CAPPOTTO Jan. 5, '1965 IMPRESSION CONTROL MECHANISM IN POWER DRIVEN TYPEWRITERS .3 Sheets-Sheet 1' Filed Sept. 29. 196} mm vm s QQ wk m \Muw k Ms mm 1 1 N: x m 3m /ws Q9 mm I o I mm o:

INVENTOR.

Samuel D. Cuppoflo Jan. 5, 1965 s. D. CAPPOTTO 3,164,237 IMPRESSION CONTROL MECHANISM IN POWER DRIVEN TYPEWRITERS Filed Sepi. 29, 1961 5 Sheets-Sheet 2' INVENTOR. Samuel D Coppotto BYQMI% 7/ AH nevs 3,164,237 IMPRESSION CONTROL MECHANISM IN POWER DRIVEN TYPEWRITERS Filed Sept. 29, 1961 Jan. 5, 1965 s. D. cAPPoT'ro a "Sheets-Sheet s Illllli 7/1.

INVENTOR Samuel D. Coppotto Mfl/ ATTORNEY S United States Patnf ()fific Patented Jan. 5,

3,164,237 IMPRESSION CONTROL MEOHANISM IN POWER DRIVEN TYPEWRITERS Samuel D. Cappotto, Syracuse, N.Y., assignor to SCM Corporation, a corporation of New York Filed Sept. 29, 1961, Ser. No. 141,794 9 Claims. (Cl. 197-17) This invention relates to power driven typewriters and, more specifically, to a control for varying the rotative speed of typewriter power rolls to thereby regulate the type impression so that differing numbers of copies of optimum legibility may be produced.

As is well known to those familiar with the employment and operation of typewriters, it is often desirable to simultaneously produce a number of copies of typewritten material. The number of copies desired will vary from one up to the maximum number that can be made by the machine, this number being seventeen in one typewriter employing an impression control mechanism constructed in accordance with the principles of the present invention. It is apparent that as the number of copies produced is increased the impression of the type characters must be made heavier. On the other hand, if the impression is too heavy for the number of copies being made the copies will have less than optimum legibility and, in extreme cases, may be entirely illegible because of smudging. Accordingly, it is the common practice to provide typewriters with a control for varying the impression in accordance with the number of copies to be made.

In the conventional typewriter, the type impression control is a serrate-surfaced dial which must be rotated against the force exerted by a spring or friction detent to change the impression. Such dials are somewhat uncomfortable to touch, especially with the force necessary to overcome the typical holding detent.

Another impression control heretofore employed consists of an adjustable lever mounted on the end of the typewriter carriage. This type of control is relatively inaccessible and is, therefore, inconvenient to operate.

A third type of impression control is commonly found in power driven typewriters and is exemplified by United States Patents 2,573,197 issued to H. J. Hart October 30, 1951, for Power-Driven Mechanism for Operating Type Bars and Other lnstrumentalities of Typewriters or Like Machines; 2,734,613 issued to C. H. Kennedy, Jr., et al. February 14, 1956, for Power Mechanism for Typewriting Machines; and 2,921,660 issued to J. P. Barkdoll January 19, 1960, for Power Driving Mechanism for Instrumentalities of Typewriters. Typically, this type of impression control consists of a rotatable impression control knob mounted adjacent the keyboard on the front casing plate of the typewriter and connected through a complicated mechanical linkage to a split pulley rota tively fixed to the power roll. The input pulley is connected by a V-belt to the typewriter motor and is, therefore, operative to rotate the power roll. By rotating the casing mounted impression control knob, the halves of the split pulley are caused to move toward or away from each other to respectively slow down or speed up the power roll. By contracting the split pulley and slowing down the power roll, the momentum imparted to the type character mounting type bars is decreased and the impressions produced by the type characters are lightened. Conversely, expanding the split pulley and speeding up the power roll increases the momentum imparted to the type bars and deepens the impression produced by the type bar mounted type characters.

As was pointed out above, by rotating the casing mounted impression control knob, the two halves of the split pulley may be caused to move toward each other to slow down the power roll and decrease the type character impression. But, in so rotating the impression control knob, suflicient force must be exerted to move the V-belt away from the rotational axis of the pulley against its natural inclination to move in the opposite direction. Either an undesirably large force must be exerted or a complicated linkage must be interposed between the impression control knob and the split pulley to create a large mechanical advantage.

In view of the state of the art as discussed above, the primary objects of this invention include:

(1) The provision of improved impression control mechanisms for power driven typewriters;

(2) The provision of improved power driven typewriters wherein the typist may quickly and conveniently adjust the machine to produce a desired number of copies by merely exerting a light finger tip force on a key button;

(3) The provision of power driven typewriters having improved impression control mechanisms wherein power derived from the power roll is utilized to collapse or expand a split power roll drive pulley to increase and decrease the speed of the power roll and, therefore, deepen and lighten the impressions produced by type characters mounted upon type bars actuated by the power roll; and

(4) The provision of improved power driven typewriters having impression controls which are conveniently located and are not unpleasant to touch.

In the present invention, these objects are attained by coupling anactuator to the ower roll shaftand employing it to drive a ratchet wheel. A push button mounted on the keyboard may be depressed to connect the actuator in driving relationship to the ratchet wheel. As the actuator rotates the ratchet wheel, it also causes a cam rigidly fixed to the ratchet wheel to rotate. A cam follower, operated by the cam, pivots a control arm to which it is operatively connected about a point intermediate its ends. The opposite end of the control arm abuts a thrust bearing which bears against one half of the split power roll drive pulley. As the control arm is pivoted by the cam follower, it allows the one half of the split pulley to move away from the other. The power roll, therefore, speeds up and heavier impressions are produced by the type characters.

The periphery of the rotating ratchet wheel is provided with a series of evenly spaced, consecutive numbers. As the wheel rotates, the numbers appear opposite a window incorporated into the push button to indicate the number of copies which the machine is set to produce. When the desired number appears in the window, the typist simply releases the push button and the actuator is automatically disconnected from the ratchet wheel.

The cam is constructed so that when the ratchet wheel is rotated past the maximum number thereon the cam will cause the follower to pivot the control arm 'to move the one half of the split pulley the maximum distance toward the other. The power roll will rotate at its minimum speed, producing the lightest impression, and the dial will indicate that the machine is set to produce the minimum number of copies.

Further novel features and other objects of this invention will become apparent from the following detailed description, discussion and the appended claims taken in conjunction with the accompanying drawings showing a preferred structure and embodiment, in which:

FIGURE 1 is a side elevation of a power driven typewriter incorporating an impression control mechanism constructed in accordance with the principles of the present invention;

FIGURE 2 is a side elevational view of the impression control mechanism showing the impression control button in the depressed or operative position;

FIGURE 3 is a perspective view of the impression control mechanism showing the impression control buttbn; in the inoperative or rest posit-ion;

V FIGURE 4 is a side elevational view of a portion of the impression control mechanism showing the path the actuator follgws in. engaging the teeth of the ratchet wheel;

FIGURE 5 is a sectional view of the split pulley control uhit with certain parts being shown in full lines to better indicate their interrelationship and is taken substantially along line 55 of FIGURE 3;

FIGURE 6 is a partial view of the split pulley control unit taken substantially along line 66 of FIGURE 2; and,

FIGURE 7 is a side view to a reduced scale of the split pulley taken substantially along line 7-7 of FIGURE 5.

Referring now to the drawings, FIGURE 1 illustrates a typewriter 10 incorporating a novel power-operated impression control mechanism 12 constructed in accordance with the principles of the present invention. Typewriter ltl includes a pair of laterally spaced apart side frames 14 (only one of which is shown) between which is mounted a power roll (not shown) rota-tively fixed to a power roll shaft 16. The power roll is rotatable by a split pulley 18 mounted on shaft 16 and coupled by a v-rbelt drive Zll to the drive pulley 22 of a constant speed electric motor 24. Impression control mechanism 12 is operated by power 'roll shaft 16 and is activatable by a keyboard mounted push button 26 to expand and contract the split pulley 18 to thereby speed up or slow down the power roll. The typewriter also includes conventional type character mounting type bars (not illustrated) which may be connected to the power roll in transitory driving relationship by depression of typewriter key buttons to propel the type characters against the print receiving surface. This arrangement is conventional and is illustrated in detail in the patent to Kennedy, Jr. et al. referred to above to which reference may be had if it is deemed necessary for a complete understanding of the present invention.

As is shown in FIGURE 1, Vbelt drive 20 includes a V-belt 28 connecting motor drive pulley 22 to an intermediate pulley Stl mounted on an intermediate shaft 32 and rotatable therewith. Intermediate shaft 32 extends between and is journalled for rotational movement by typewriter side frames 14. A spring-biased split pulley 34, rotatively fixed to intermediate shaft 32-, is connected by a second V-belt 36 to the split power roll drive pulley 18. Split pulley 34 expands as split pulley 18 contracts and contracts as split pulley 18 expands so that V-belt 36, at all times, travels through a path of constant length and is thereby maintained under constant tension.

Looking next to FIGURE 5, one half 38 of the split power roll drive pulley 18 is staked to a collar 40 journal-led on power roll shaft 16. A pair of 90 spaced apart set screws 42 (only one of which is shown) extend through drilled and tapped holes 44 in collar all into engagement with power roll shaft 16 to rotatively and axially fix split pulley half 38 to the shaft. Shaft 16 is provided with elongated flat-bottom screw receiving recesses 46 (only one of which is shown) to make more effective the holding effect of set screws 42.

The other half 48 of split pulley 18 is staked to a sleeve 50 within which is press fitted a sleeve bushing 52. Bushing 52 is slidab'ly mounted on power roll shaft 16, the limits of its travel being determined by its engagement with the inner end of longitudinally opening annular recess 54 in collar 40 and its engagement with an eccentric 56 mounted in abutting relationship to the end of sleeve 50 for rotation therewith. Eccentric 56 is secured in place by a preferably nylon washer 58 and a screw 6b which extends through washer 58 and eccentric 56 into threaded engagement with a drilled and tapped hole 62 in the end of power roll shaft 16. Thus, as sleeve 52 is moved axially on power roller shaft 16, the pulley half 48 is moved toward and away from the axially fixed pulley half 33 to vary the effective diameter of split pulley 18, and, therefore, the speed of the power roll and the impression produced by the type bar mounted type characters.

The pulley halves 38 and 48 are rotatively fixed to one another by the arrangement shown in FIGURE 7. Equiangular-ly spaced tabs 64 are struck out of pulley half 38 and extended through slots 66 in pulley half 43 into abutting engagement with the ends thereof. Similar tabs 63 are struck out of pulley half 48 and extended through slots 7% in pulley half 3% in abutting relationship therewith. While this arrangement precludes relative rotational movement of pulley halves 38 and 48, it does not prevent movable pulley half 48 from being axially displaced with respect to the axially fixed pulley half 33.

Returning now to FIGURE 5, eccentric S6 constitutes the power input for the power operated impression control mechanism 12. Eccentric 56, which is preferably fashioned from nylon, has a main body portion 72 of comparatively large diameter and an integral, laerally extending crank portion 74 of relatively small diameter. An elongated actuator 76 is rotatively mounted on eccentric crank 74 and is laterally positioned by body portion 2 of eccentric 56 and nylon washer 58. As sleeve Ell is rotated by power roller shaft 16, it rotates eccentric 56 which imparts an elliptical motion to the actuator 76.

Actuator 76 extends from eccentric 56 toward the front of typewriter 10 and rests, adjacent its forward end, on a preferably nylon roller 7%} rotatably mounted on a stud 89 which is fixed to an upstanding projection 32 on a depending L shaped arm 84 attached to impression control button 26. A spring 86 is connected between the forward end of actuator '76 and an integral portion lint the lower end of L-shaped arm 84 to bias actuator 76 into engagement with nylon roller 7 S.

The impression control button 26 to which the L-shaped arm 84 is attached is mounted on the forward end of a lever 90. Lever 9t is pivotally mounted, intermediate its ends, on a stud 92 attached to the end of an upwardly and rearwardly extending arm 94 of a bracket E6. As is best shown in FIGURES l and 2, bracket as is rigidly attached to side frame 14 by screws 98.

Impression control button 26 is biased against a laterally extending projection or stop 1% on bracket arm 94 (this is the inoperative or rest position of FIGURE 3) by a spring 102 connected between the rear end of lever 96) and a laterally extending spring mounting projection 164 on bracket arm 94.

When it is desired to vary the impression being produced by the type characters in order to make a difierent number of copies, actuator 76 is rotated clockwise by de pressing impression control button 26 until the laterally extending stop 106 on L-shaped arm 84 engages the upper surface of side frame 14.

This lowers a laterally extending pawl 168 on actuator 76 to a position where it, due to the elliptical motion imparted to actuator 7'5 by eccentric 56, will rotate a ratchet wheel 110 in a counterclockwise direction since pawl M8, in this lowered position, engages internal teeth 112 on the ratchet wheel. Ratchet wheel 110 is rotatively mounted on a shaft 114 which is journal-led on side frame 14.

It will be remembered that eccentric crank 74 causes actuator 76 to follow an elliptical path. Because of the actuator support arrangement described above, pawl 168 will follow a similar path of lesser amplitude. The path followed by pawl 1% as it is moved through one cycle by eccentric crank 7 4 is shown in FIGURE 4. Pawl 108 first engages the tooth 112 at position A and moves forwardly to position B where it fully engages the tooth. Pawl 108 then continues to move forward, moving the tooth 112 with it (and thus spacing ratchet wheel lit] counterclockwise) until the pawl reaches its most forward position C.

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P'azwl 108 then travels rearwardly, disengaging from tooth 112 and passing through position D to the rearmost tooth engaging position A. Pawl 108 will repeat this cycle so long as impression control button 26 is depressed.

The outer periphery of ratchet wheel 110 is numbered from one to seventeen proceeding in a clockwise direction (the opposite direction from which it is rotated by pawl 108). As ratchet wheel 110 is rotated, these numbers will appear opposite a transparent window 116 provided in the rear end of impression control button 26 through which they may be read to determine the number of copies that the machine is set to produce. When the desired number appears opposite the window, the typist simply releases impression control button 26. Spring 102 biases button mounting lever 90 counterclockwise until it engages stop 100, raising pawl 108 out of engagement with ratchet wheel teeth 112.

Ratchet wheel 110 is prevented from moving clockwise by a detent 118 longitudinally adjustably mounted on a control arm 120 by screws 122. As is best shown in FIGURE 3, detent spring 118 has a laterally extending arm 124 which is continuously biased into engagement with ratchet wheel teeth 112 by the spring-forming configuration of the detent.

Laterally extending ears 126 formed intermediate the detent mounting control arm 120 adjacent the top and bottom edges thereof are disposed adjacent laterally extending arms 128 of a bracket 139 attached to side frame 14 by screws 132 to vertically support the control arm 120. A shaft 134 extends through the control arm ears 126 and the bracket arms 128 to pivotally mount control arm 120 with respect to the bracket 130.

Also pivotally mounted on shaft 134 is an adjuster 136 connected in spaced angular relationship to control arm 120 by an adjusting screw 138 and a lock nut 140. Adjuster 136 extends forwardly and mounts, on a laterally extending integral projection 142 at its forward end, a stud 144 on which is journalled a rotatable cam follower 146.

Cam follower 146 engages the cam surface 148 of a cam 150 rotatively fixed to ratchet wheel 110. As ratchet wheel 110 and cam 150 are spaced by actuator 76, cam

follower 146, following cam surface 148, pivots adjuster 136 and control arm 120 counterclockwise about shaft 134. The rear end of control arm 120 (see FIGURES 5 and 6) surrounds the collar mounting the movable half 48 of split pulley 18 and abuts thrust bearing 152 rotatively mounted on the collar. A pin 154 mounted on thrust bearing 152 extends through a slot 156 in control arm 120 to prevent the thrust bearing from rotating on collar 50.

As V-belt 36 travels about split pulley 18 under tension, it tends to move the movable half 48 of split pulley 18 away from the fixed half 38. This, in turn, tends to move thrust bearing 152 to the left and, therefore, to move control arm 120 and adjuster 136 counterclockwise about shaft 134 to bias arm follower 146 into engagement with cam surface 143 of cam 150. Cam surface 148 is arranged so that as ratchet wheel 110 rotates counterclockwise, the above described movement may occur. As a result, as the ratchet wheel Mil-rotates, the split pulley halves move further apart and the speed of the power roller increases and, therefore, the type impression is made heavier. Simultaneously, numbers of increasing magnitude appear opposite the window 116 in impression control button 2-6.

Just after number 17 appears opposite window 116, a relatively sharp increase or rise on cam surface 148 engages cam follower 146 and rotates adjuster 136 and control arm 12% clockwise about shaft 134. At this point, split pulley 122 is closed to its minimum width, the power roll rotates at its minimum speed to produce the lightest type character impression, and the lowest number on the periphery of rachet wheel 110 appears opposite the window 116 in push button 26.

6 *In summary then, the operation of the impression con trol mechanism provided by the present invention is as follows: Power roll shaft 16 is continuously rotated by motor 24 to which it is connected by V-belt drive 20. As the power roll shaft 16rotates, it rotates eccentric 56 to impact continuous elliptical motion to actuator 76. When it is desired to vary the impression of the type characters to make a different number of copies of typewritten material, the impression control button 26 is depressed. This moves actuator 76 downwardly until pawl 108 engages one of the teeth 112 of the ratchet wheel 110. Actuator 76, being thus engaged, spaces ratchet wheel in a counterclockwise direction. Cam 150, being attached to ratchet wheel 110, rotates in the same direction. As cam 1549 rotates, it engages cam follower 146 which follows a path that allows adjuster 136 and control arm to be biased in a counterclockwise direction by the action of V-belt 36. This, in turn, allows the movable half 48 of split pulley 18 to move to the left, permitting V-belt 36 to move inwardly in pulley 18 since the effective diameter of the latter is decreased as the pulley halves 38 and 48 move further apart. As a result, the power roll is speeded up and, for the reasons explained above, the type characters will produce a heavier impression. At the same time, numbers of increasing magnitude formed on the periphery of ratchet wheel 118 will appear opposite the window 116 in push button 26. be remembered, are indicative of the number of copies of optimum legibility which will be produced by the machine with the power roll rotating at a particular speed. When the number indicative of the desired number of copies appears opposite window 116, the operator releases push button 26. Biasing spring 102 then rotates push button 26 in a counterclockwise direction about pivot stud 92. As impression control button 26 moves counterclockwise, i.e., upwardly, it raises L-shaped arm 84 causing roller '78 to bear against the lower surface of actuator 76 to raise the latter. As the forward end of actuator 76 moves upwardly, pawl 108 disengages from the teeth 112 of ratchet wheel 110 and the ratchet wheel and cam cease to rotate. The power roll will continue to rotate at the speed necessary to produce the desired number of copies until the operator again depresses push button 226 to further rotate the ratchet wheel 110. Actuator 76, being continuously engaged withpower roll drive shaft 16, will continue to follow its elliptical path. Since it contacts only nylon bearing surfaces, this operation will be essentially noiseless.

Shortly after number 17 (which is indicative, in one typewriter embodiment, of the maximum number of copies the machine can produce) appears opposite window 116, a sharp increase on cam surface 148 of cam 150 will be engaged by cam follower 146. This sharp increase, acting against cam follower 146, rotates adjuster 136 and control arm 120 in a clockwise direction. Thrust bearing .152 is forced to the right, moving the movable half 48 of split pulley 18 to the right and contracting split pulley 18 to the minimum width. As a result, the power roll is slowed to its minimum speed thereby producing the lightest type character impression. At the same time, the number of least magnitude appears opposite the window 116 in push button 26.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A type impression regulator for a power driven These numbers, it will.

typewriter'comprising: a type element actuating rotatable power member, constant speed power source means connected in driving relationship to said power member, means engageable with said power member and adapted to be driven thereby for varying the speed ratio between said power source means and said power member, and selectively and manually operable means effective when operated to 'drivingly engagesaid last-stated means to said power member to incrementally actuate said speed ratio varying means and variably set the speed ratio on release of said manually operable means.

2. Uniform impression control adjustment mechanism for power driven typewriters, comprising: a type element actuating rotatable power member having variable diameter pulley means including relatively axially displaceable pulley halves mounted on one end thereof, constant speed power source means including a fixed diameter drive pulley, belt drive means operably connected between said drive pulley and said variable diameter pulley means, and means for varying the effective diameter of said variable diameter pulley means to thereby vary the speed ratio between said power member and said power source means including means engageable with said rotatable power member and adapted to be driven thereby for varying the distance between said pulley halves and selectively and manually operable means effective when operated to drivingly engage said last-stated means to said power member to incrementally actuate said speed ratio varying means and variably set the speed ratio on release of said manually operated means.

3. Uniform impression control adjustment mechanism for power driven typewriters, comprising: a type element actuating rotatable power member having a split pulley mounted on one end thereof, constant speed power source means operably connected to said split pulley, said power source being continuously operated while activated, a continuously operated motion transmitting member, means operably connecting said power member to said motion transmitting member, means operable by said motion transmitting member to vary the effective diameter of said split pulley, and means for selectively connecting said motion transmitting member in operative relationship to said diameter varying means to incrementally activate said diameter varying means and variably set the effective diameter of said pulley on release of said manually operable means.

4. Uniform impression control adjustment mechanism fora power driven typewriter, comprising: a type element actuating rotatable power member having a split pulley mounted on one end thereof, constant speed power source means operably connected to said pulley, a rotary member provided with a plurality of internal teeth, a motion transmitting member continuously operated by said power member and having a portion arranged to engage one of said internal teeth and thereby move said rotary member a preselected angular distance for each revolution of said power member, means operated by said rotary member for varying the effective diameter of said split pulley as said rotary member is rotated, and means for selectively connecting said motion transmitting member in driving relationship to the internal teeth of said rotary member.

5. Uniform impression control adjustment mechanism as set forth in claim 4, wherein said diameter varying means, means includes a cam rotatable with said rotary member, an adjusting member pivoted intermediate its ends and having one end operatively associated with one of the halves of said split pulley, a cam follower mounted on the opposite end of said adjusting member, and means biasing said follower into engagement with the cam surface of said cam.

6. Uniform impression control adjustment mechanism as set forth in claim 4, wherein the periphery of said rotary member is provided with evenly spaced consecutive numbers and window means are disposed in spaced relation to said periphery, whereby the number appearing opposite said window is indicative of the effective diameter of said split pulley and, therefore, of the speed of said power member and the impressions produced by the type characters.

7. Uniform impression control adjustment mechanism as set forth in claim 5, wherein said adjusting member is apertured adjacent said one end and including a bushing slidabie on said power roll member, a sleeve on said bushing and rotatably fixed to said one pulley half, said sleeve extending through the aperture in said adjusting member and having an annular shoulder formed thereon, and a thrust bearing surroundin said sleeve and interposed between said shoulder and said adjusting member.

8. Uniform impression control adjustment mechanism for a power driven typewriter, comprising: a type element actuating rotatable power member having a split pulley mounted on one end thereof; constant speed power source means operably connected to said puliey; a rotary member provided with a plurality of internal teeth; a motion transmitting member continuously operated by said power member and having a portion arranged to engage one of said internal teeth and thereby move said member a pre-selected angular distance for each revolution of said power member; means arranged to bias said member into engagement with said teeth; means operated by said rotary member for varying the effective diameter of said split pulley as said rotary member is rotated; and means for selectively connecting said motion transmitting member in driving relationship to the internal teeth of said rotary member, said connecting means including a pivoted key member and means biasing said motion transmitting member to an inoperative position wherein said key member precludes said motion transmitting member biasing means from biasing said motion transmitting memher into engagement with said teeth, said key member being selectively pivotable to an alternative operative position wherein said motion transmitting member biasing means may bias said motion transmitting member into engagement with said teeth.

9. Uniform impression control adjustment mechanism as set forth in claim 3, wherein said motion transmitting member has an aperture adjacent one end thereof and including an eccentric rotatably fixed to said power member having a crank portion extending through the aperture in said motion transmitting member, and including means fixing said member on said crank portion.

References Cited in the file of this patent UNITED STATES PATENTS 

8. UNIFORM IMPRESSION CONTROL ADJUSTMENT MECHANISM FOR A POWER DRIVEN TYPEWRITER, COMPRISING: A TYPE ELEMENT ACUTATING ROTATABLE POWER MEMBER HAVING A SPLIT PULLEY MOUNTED ON ONE END THEREOF; CONSTANT SPEED POWER SOURCE MEANS OPERABLY CONNECTED TO SAID PULLEY; A ROTARY MEMBER PROVIDDED WITH A PLURALITY OF INTERNAL TEETH; A MOTION TRANSMITTING MEMBER CONTINUOUSLY OPERATED BY SAID POWER MEMBER AND HAVING A PORTION ARRANGED TO ENGAGE ONE OF SAID INTERNAL TEETH AND THEREBY MOVE SAID MEMBER A PRE-SELECTED ANGULAR DISTANCE FOR EACH REVOLUTION OF SAID POWER MEMBER; MEANS ARRANGED TO BIAS SAID MEMBER INTO ENGAGEMENT WITH SAID TEETH; MEANS OPERATED BY SAID ROTARY MEMBER FOR VARYING THE EFFECTIVE DIAMETER OF SAID SPLIT PULLEY AS SAID ROTARY MEMBER IS ROTATED; AND MEANS FOR SELECTIVELY CONNECTING SAID MOTION TRANSMITTING MEMBER IN DRIVING RELATIONSHIP TO THE INTERNAL TEETH OF SAID ROTARY MEMBER, SAID CONNECTING MEANS INCLUDING A PIVOTED KEY MEMBER AND MEANS BIASING SAID MOTION TRANSMITTING MEMBER TO AN INOPERATIVE POSITION WHEREIN SAID KEY MEMBER PRECLUDES SAID MOTION TRANSMITTING MEMBER BIASING MEANS FROM BIASING SAID MOTION TRANSMITTING MEMBER INTO ENGAGEMENT WITH SAID TEETH, SAID KEY MEMBER BEING SELECTIVELY PIVOTABLE TO AN ALTERNATIVE OPERATIVE POSITION WHEREIN SAID MOTION TRANSMITTING MEMBER BIASING MEANS MAY BIAS SAID MOTION TRANSMITTING MEMBER INTO ENGAGEMENT WITH SAID TEETH. 